R/ALGO__GSA.R

In EmiR: Evolutionary Minimizer for R

###############################################################################
# Emir: EmiR: Evolutionary minimization forR                                  #
# Copyright (C) 2021 Davide Pagano & Lorenzo Sostero                          #
#                                                                             #
# This program is free software: you can redistribute it and/or modify        #
# it under the terms of the GNU General Public License as published by        #
# the Free Software Foundation, either version 3 of the License, or           #
# any later version.                                                          #
#                                                                             #
# This program is distributed in the hope that it will be useful, but         #
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY  #
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License    #
# for more details: <https://www.gnu.org/licenses/>.                          #
###############################################################################


#' Configuration object for the Gravitational Search Algorithm
#'
#' Create a configuration object for the Gravitational Search Algorithm (GSA). At minimum the number of iterations
#' (parameter `iterations`) and the number of planets (parameter `population_size`) have
#' to be provided.
#'
#' @param iterations maximum number of iterations.
#' @param population_size number of planets.
#' @param iterations_same_cost maximum number of consecutive iterations with the \emph{same}
#' (see the parameter `absolute_tol`) best cost before ending the minimization. If `NULL` the
#' minimization continues for the number of iterations specified by the parameter `iterations`.
#' Default is `NULL`.
#' @param absolute_tol absolute tolerance when comparing best costs from consecutive iterations.
#' If `NULL` the machine epsilon is used. Default is `NULL`.
#' @param grav gravitational constant, involved in the acceleration of planets.
#' Default is `100`.
#' @param grav_evolution parameter to control the exponentially decreasing gravitational constant with
#' the iterations. Default is `20.0`.
#' @return `config_gsa` returns an object of class `GSAConfig`.
#' @importFrom Rdpack reprompt
#' @references \insertRef{Rashedi2009}{EmiR}
#' @export
#'
#' @examples
#' conf <- config_gsa(iterations = 100, population_size = 50, iterations_same_cost = NULL,
#' absolute_tol = NULL, grav = 1000, grav_evolution = 20.)
#'
config_gsa <- function(iterations,
                      population_size,
                      iterations_same_cost = NULL,
                      absolute_tol         = NULL,
                      grav                 = 1000,
                      grav_evolution       = 20.) {
  p <- new("GSAConfig")
  commonOpt              <- checkCommonConfigOptions(iterations, population_size, iterations_same_cost, absolute_tol)
  p@iterations           <- commonOpt$iterations
  p@population_size      <- commonOpt$population_size
  p@iterations_same_cost <- commonOpt$iterations_same_cost
  p@absolute_tol         <- commonOpt$absolute_tol

  p@grav               <- grav
  p@grav_evolution     <- grav_evolution
  return(p)
}

check_algo_options_gsa <- function(p, ...) {
  config_options <- list(...)
  if (length(config_options) == 0) return(p)
  for (i in 1:length(config_options)) {
    if (names(config_options[i]) == "grav") {
      p@grav            <- config_options[[i]]
    } else if (names(config_options[i]) == "grav_evolution") {
      p@grav_evolution            <- config_options[[i]]
    } else {
      stop(paste0("Unknown option '", names(config_options[i]), "' for algorithm GSA."))
    }
  }
  return(p)
}